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vfs: factor out inode_insert5()
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Split out common helper for race free insertion of an already allocated
inode into the cache.  Use this from iget5_locked() and
insert_inode_locked4().  Make iget5_locked() use new_inode()/iput() instead
of alloc_inode()/destroy_inode() directly.

Also export to modules for use by filesystems which want to preallocate an
inode before file/directory creation.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Miklos Szeredi authored and Miklos Szeredi committed May 31, 2018
1 parent b148cba commit 80ea09a
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Showing 2 changed files with 79 additions and 89 deletions.
164 changes: 75 additions & 89 deletions fs/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1002,6 +1002,70 @@ void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
}
EXPORT_SYMBOL(unlock_two_nondirectories);

/**
* inode_insert5 - obtain an inode from a mounted file system
* @inode: pre-allocated inode to use for insert to cache
* @hashval: hash value (usually inode number) to get
* @test: callback used for comparisons between inodes
* @set: callback used to initialize a new struct inode
* @data: opaque data pointer to pass to @test and @set
*
* Search for the inode specified by @hashval and @data in the inode cache,
* and if present it is return it with an increased reference count. This is
* a variant of iget5_locked() for callers that don't want to fail on memory
* allocation of inode.
*
* If the inode is not in cache, insert the pre-allocated inode to cache and
* return it locked, hashed, and with the I_NEW flag set. The file system gets
* to fill it in before unlocking it via unlock_new_inode().
*
* Note both @test and @set are called with the inode_hash_lock held, so can't
* sleep.
*/
struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
int (*test)(struct inode *, void *),
int (*set)(struct inode *, void *), void *data)
{
struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
struct inode *old;

again:
spin_lock(&inode_hash_lock);
old = find_inode(inode->i_sb, head, test, data);
if (unlikely(old)) {
/*
* Uhhuh, somebody else created the same inode under us.
* Use the old inode instead of the preallocated one.
*/
spin_unlock(&inode_hash_lock);
wait_on_inode(old);
if (unlikely(inode_unhashed(old))) {
iput(old);
goto again;
}
return old;
}

if (set && unlikely(set(inode, data))) {
inode = NULL;
goto unlock;
}

/*
* Return the locked inode with I_NEW set, the
* caller is responsible for filling in the contents
*/
spin_lock(&inode->i_lock);
inode->i_state |= I_NEW;
hlist_add_head(&inode->i_hash, head);
spin_unlock(&inode->i_lock);
unlock:
spin_unlock(&inode_hash_lock);

return inode;
}
EXPORT_SYMBOL(inode_insert5);

/**
* iget5_locked - obtain an inode from a mounted file system
* @sb: super block of file system
Expand All @@ -1026,66 +1090,18 @@ struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
int (*test)(struct inode *, void *),
int (*set)(struct inode *, void *), void *data)
{
struct hlist_head *head = inode_hashtable + hash(sb, hashval);
struct inode *inode;
again:
spin_lock(&inode_hash_lock);
inode = find_inode(sb, head, test, data);
spin_unlock(&inode_hash_lock);
struct inode *inode = ilookup5(sb, hashval, test, data);

if (inode) {
wait_on_inode(inode);
if (unlikely(inode_unhashed(inode))) {
iput(inode);
goto again;
}
return inode;
}
if (!inode) {
struct inode *new = new_inode(sb);

inode = alloc_inode(sb);
if (inode) {
struct inode *old;

spin_lock(&inode_hash_lock);
/* We released the lock, so.. */
old = find_inode(sb, head, test, data);
if (!old) {
if (set(inode, data))
goto set_failed;

spin_lock(&inode->i_lock);
inode->i_state = I_NEW;
hlist_add_head(&inode->i_hash, head);
spin_unlock(&inode->i_lock);
inode_sb_list_add(inode);
spin_unlock(&inode_hash_lock);

/* Return the locked inode with I_NEW set, the
* caller is responsible for filling in the contents
*/
return inode;
}

/*
* Uhhuh, somebody else created the same inode under
* us. Use the old inode instead of the one we just
* allocated.
*/
spin_unlock(&inode_hash_lock);
destroy_inode(inode);
inode = old;
wait_on_inode(inode);
if (unlikely(inode_unhashed(inode))) {
iput(inode);
goto again;
if (new) {
inode = inode_insert5(new, hashval, test, set, data);
if (unlikely(inode != new))
iput(new);
}
}
return inode;

set_failed:
spin_unlock(&inode_hash_lock);
destroy_inode(inode);
return NULL;
}
EXPORT_SYMBOL(iget5_locked);

Expand Down Expand Up @@ -1426,43 +1442,13 @@ EXPORT_SYMBOL(insert_inode_locked);
int insert_inode_locked4(struct inode *inode, unsigned long hashval,
int (*test)(struct inode *, void *), void *data)
{
struct super_block *sb = inode->i_sb;
struct hlist_head *head = inode_hashtable + hash(sb, hashval);
struct inode *old = inode_insert5(inode, hashval, test, NULL, data);

while (1) {
struct inode *old = NULL;

spin_lock(&inode_hash_lock);
hlist_for_each_entry(old, head, i_hash) {
if (old->i_sb != sb)
continue;
if (!test(old, data))
continue;
spin_lock(&old->i_lock);
if (old->i_state & (I_FREEING|I_WILL_FREE)) {
spin_unlock(&old->i_lock);
continue;
}
break;
}
if (likely(!old)) {
spin_lock(&inode->i_lock);
inode->i_state |= I_NEW;
hlist_add_head(&inode->i_hash, head);
spin_unlock(&inode->i_lock);
spin_unlock(&inode_hash_lock);
return 0;
}
__iget(old);
spin_unlock(&old->i_lock);
spin_unlock(&inode_hash_lock);
wait_on_inode(old);
if (unlikely(!inode_unhashed(old))) {
iput(old);
return -EBUSY;
}
if (old != inode) {
iput(old);
return -EBUSY;
}
return 0;
}
EXPORT_SYMBOL(insert_inode_locked4);

Expand Down
4 changes: 4 additions & 0 deletions include/linux/fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2879,6 +2879,10 @@ extern struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
int (*test)(struct inode *, void *), void *data);
extern struct inode *ilookup(struct super_block *sb, unsigned long ino);

extern struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
int (*test)(struct inode *, void *),
int (*set)(struct inode *, void *),
void *data);
extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
extern struct inode * iget_locked(struct super_block *, unsigned long);
extern struct inode *find_inode_nowait(struct super_block *,
Expand Down

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